The invention relates to a metallic object comprising a stable coating of nucleic acid compounds, i.e. nucleic acids and/or nucleic acid derivatives, and a method for manufacturing aforementioned coating. By coupling active ingredients to the nucleic acids and/or nucleic acid derivatives, the coating can be matched to different applications and the biocompatibility of surfaces modified accordingly can be increased.
Such coated metals are of interest for the medical field and veterinary medicine, for example, for implants but also for different fields of biotechnology as well as chip and sensor technology.
An efficient immobilization of nucleic acids and nucleic acid derivatives on solid support materials is of great importance for many areas of biotechnology.
Methods for the immobilization of nucleic acids on glass, for example, for producing nucleic acid arrays, as well as for the immobilization of gold pobjects (U.S. Pat. No. 6,291,188 B1, EP 1170374 A1), for example, for gene transfer, are known. The immobilization of gold pobjects is realized in this context either by adsorption (EP 1170374 A1) or by a sulfur linker (U.S. Pat. No. 6,291,188 B1).
Moreover, methods for adsorption of nucleic acids on zirconium(IV) oxide and aluminum oxide and other metal oxides are disclosed (DE 4309248 A1, EP 0391 608 A2, WO 92/18514 A1). In order to ensure this adsorption on the aforementioned metal oxides, the material, however, must be comprised of at least 50%, preferably 99%, of metal oxide (EP 0391 608 A2, p. 4, lines 18-29).
For numerous applications, an oriented, reproducible, permanent, fixed, chemical and temperature-resistant bonding of the nucleic acids and/or nucleic acid derivatives on the substrate surface is desirable.
Disclosed are also methods for bonding oligonucleotides on valve metals, for example, silanized tantalum (Bier, F. F., and Scheller, F. W., 1996, Biosensors & Bioelectronics 11:669-674) and silanized titanium (Bier, F. F., et al., 1999, Biotechniques 27:752-760). In order to achieve the silanization of the metal surface required for this method, the metal must be pretreated under aggressive chemical conditions (see also Xiao, S. J. et al., 1998, Langmuir, 14:5507-5516). Disadvantageously, these methods are comprised of at least three steps. In addition, the nucleic acids must also be modified in a complex procedure.
Methods are know that ensure a fixed connection of organic molecules, for example, collagen, on valve metal surfaces (DE 19643555). Oxide layers that are formed on such metals or alloys exhibit ion conduction at least under anodic polarization and enable thus by means of anodic polarization a variation of oxide layer thickness within wide limits. For this purpose, the phenomenon that for anodic polarization in aqueous solutions the already present oxide layer on titanium materials begins to grow by migration of ions within the electric field is utilized. Into this growing layer, molecules or functional groups that are present on the surface, for example, as a result of adsorption can be incorporated into the oxide layer. However, an oriented incorporation by means of defined molecular areas (regiospecific incorporation) of substances and thus maintaining certain properties/functions of the substances cannot be realized.
It is known in connection with inorganic ions, primarily phosphate, that they can be incorporated into such anodically growing titanium(IV) oxide layers. In this connection, the anion can possibly also be part of larger molecules (DE 19643555) as a functional group. In order for the molecule provided with the anionic group to be incorporated into the anodic oxide layer, the electrostatic charge conditions between surface and adsorbing molecule (part) must allow a primary adsorption.
Negatively charged molecules, such as nucleic acids, are however repelled by the titanium-titanium(IV) oxide surface that is negatively charged under physiological conditions. The method described in DE 19643555 is therefore not applicable in connection with nucleic acid molecules.
A general disadvantage of the chemically or biochemically modified surfaces employed in medicine, biology, and chemistry is the lack of variability and modularity. Substances that have been applied once remain in many cases irreversibly attached to the surfaces or have a release kinetics adjustable only to a limited extent. Moreover, the coating process must be matched often in complex ways to the desired coating. It is therefore almost impossible for a user to match a coating to his applications.